U.S. patent number 4,311,153 [Application Number 06/192,265] was granted by the patent office on 1982-01-19 for screw-in lead having lead tip with membrane.
This patent grant is currently assigned to Medtronic, Inc.. Invention is credited to Karel F. A. A. Smits.
United States Patent |
4,311,153 |
Smits |
January 19, 1982 |
**Please see images for:
( Certificate of Correction ) ** |
Screw-in lead having lead tip with membrane
Abstract
A screw-in endocardial transvenous pacing lead having a lead tip
with a sealing membrane. The lead is chronically affixed by a
helical fixation coil having a pointed tip which is rotatably
advanced through a helical lumen in the lead tip into the
endocardial tissue. During transvenous insertion, the helical
fixation coil is retracted into a chamber to protect against damage
of the vein. A sealing membrane is positioned perpendicularly
within the helical lumen of the lead tip preventing ingress of body
fluids. The sealing membrane is of silicon rubber with a
polyurethane coating on either side. Upon being properly located
within the heart, the helical fixation coil is rotatably extended.
The pointed tip of the helical fixation coil punctures the sealing
membrane normal to its direction of travel. The sealing membrane
provides a seal around the helical fixation coil.
Inventors: |
Smits; Karel F. A. A.
(Oirsbeek, NL) |
Assignee: |
Medtronic, Inc. (Minneapolis,
MN)
|
Family
ID: |
22708951 |
Appl.
No.: |
06/192,265 |
Filed: |
September 30, 1980 |
Current U.S.
Class: |
607/127;
607/128 |
Current CPC
Class: |
A61N
1/0573 (20130101) |
Current International
Class: |
A61N
1/05 (20060101); A61N 001/04 () |
Field of
Search: |
;128/784,785,419P |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kamm; William E.
Attorney, Agent or Firm: Rooney; John L. Breimayer; Joseph
F.
Claims
What is claimed is:
1. An implantable lead comprising:
a conductor having a proximal end and a distal end;
an insulator having a proximal end and a distal end;
a chamber attached to said distal end of said insulator having an
aperture;
a fixation device rotatably attached to said chamber whereby
rotation of said fixation device is a first direction causes said
fixation device to move proximal relative to said aperture and
rotation of said fixation device in a second direction causes said
fixation device to move distal relative to said aperture; and
a seal attached to said chamber at said aperture having a shape
causing a portion of said fixation device to frictionally engage
said seal in a direction substantially normal to the direction of
motion of said portion of said fixation device when said fixation
device is rotated in said first and second direction.
2. An implantable lead according to claim 1 wherein said fixation
device is a helix.
3. An implantable lead according to claim 1 wherein said seal
further comprises:
a non-stress relaxing material having a first side and a second
side; and
a covering of thermoplastic material attached to said first side
and said second side of said non-stress relaxing material.
4. An implantable lead according to claim 3 wherein said non-stress
relaxing material is silicon rubber.
5. An implantable lead according to claim 4 wherein said covering
of thermoplastic material is polyurethane.
6. An implantable lead according to claim 1, 2, 3, 4 or 5 wherein
said conductor is attached to said fixation device whereby rotation
of said conductor is said first direction causes said fixation
device to rotate in said first direction and rotation of said
conductor in said second direction causes said fixation device to
rotate in said second direction.
7. An implantable lead according to claim 1, 2, 3, 4 or 5 further
comprising:
a stylet loosely inserted within said conductor; and
means attached to said stylet and said fixation device for coupling
torque applied to said stylet to said fixation device.
8. In a screw-in endocardial pacing lead with a distal end having a
helically shaped fixation device with at least one coil and a sharp
point and having a chamber with an aperture located at said distal
end of said pacing lead into which and from which said helical coil
may be rotationally projected, the improvement comprising:
a guide seal attached to said chamber at said aperture at an angle
perpendicular to the direction of movement of said sharp point of
said helically shaped fixation device.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to medical electronic
devices and more specifically relates to cardiac pacing leads.
2. Discussion of the Prior Art
A major advance in the development of endocardial pacing leads is
taught by Bisping in U.S. Pat. No. 4,106,512. The Bisping invention
provides a helical fixation device to be screwed into the
endocardial tissue thereby securing the distal end of the lead both
acutely and chronically. A major problem with the endocardial
screw-in lead of Bisping and his successors has been obtaining a
proper seal at the distal end of the lead to prevent ingress of
body fluid into the lead body. At column 5, lines 23-27, Bisping
describes the use of a medical adhesive to effect the desired
seal.
Copending U.S. patent application Ser. No. 69,948, now abandoned,
of Dutcher, et al, assigned to the assignee of the present
invention describes a guide seal using a sealing membrane of
silicon rubber. Common to the sealing techniques taught by Bisping,
Dutcher, et al, and others studied is the problem of leakage during
chronic implantation.
SUMMARY OF THE INVENTION
The present invention involves an improved seal to greatly curtail
this leakage problem. The solution is obtained via use of a sealing
membrane of silicon rubber with a covering of polyurethane. This
"sandwich" configuration has been found to be more effective as the
sealing membrane tends to retain its resiliency over greater
angular displacement at the puncture. A second aspect is locating
the sealing membrane within the helical lumen to cause the helical
fixation coil to puncture the sealing membrane at an angle normal
to its direction of travel. This provides a more uniform
puncture.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of the screw-in lead with the helical
fixation coil extended.
FIG. 2 is a schematic view of a prior art screw-in lead tip with
helical fixation coil retracted.
FIG. 3 is a schematic view of a prior art screw-in lead tip with
helical fixation coil extended.
FIG. 4 is a schematic view of a screw-in lead tip employing the
present invention with helical fixation coil retracted.
FIG. 5 is a schematic view of a screw-in lead tip employing the
present invention with helical fixation coil extended.
FIG. 6 is a schematic view of a sealing membrane.
FIG. 7 is a front view of a screw-in lead tip.
FIG. 8 is a side sectional view of the screw-in lead tip.
FIG. 9 is a front sectional view of the screw-in lead tip.
FIG. 10 is a partial cutaway view of the sealing membrane.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is seen as being incorporated into a screw-in
lead as taught by Bisping in U.S. Pat. No. 4,106,512, which is
hereby incorporated by reference. However, it is anticipated that
the present invention will also be used with a screw-in lead
similar to that taught by Dutcher, et al, in U.S. Pat. No.
4,146,036 which is also incorporated by reference. Those of
ordinary skill in the art will be readily able to apply the present
invention to screw-in leads of other types as well.
FIG. 1 is a plan view of a screw-in lead employing the present
invention. Lead body 26 is of an insulator substantially inert to
body fluids. A conductor within lead body 26 couples connector pin
24 at the proximal end to helical fixation coil 14 at the distal
end. Lead tip 10 is inserted into the heart via well known
transvenous insertion techniques with helical fixation coil 14
totally retracted within lead tip 10 such that pointed tip 16 is
not exposed to render possible harm to tissues while in transit.
Helical fixation coil 14 may be rotatably extended or retracted by
rotation of connector pin 24. Connector body 22 serves to seal the
proximal end from ingress of body fluids upon insertion into a
pulse generator (not shown).
FIG. 2 is a highly enlarged schematic view of the distal tip of a
prior art screw-in lead. Helical fixation coil 14 is shown in the
retracted position. Sealing membrane 12a prevents ingress of body
fluids. It can be seen that upon extending helical fixation coil
14, sealing membrane 12a is punctured at point 18a producing a
puncture whose projection on sealing membrane 12a is shown as
dimension 20a. That means that sealing membrane 12a is disturbed
along dimension 20a. Member 11 is a guiding wire for extension of
the fixation coil upon rotation of the fixation coil.
FIG. 3 shows the same prior art structure after extending helical
fixation coil 14. The puncture at point 18a is in the direction of
travel of pointed tip 16. Because sealing membrane 12a is normal to
the main axis of lead tip 10, the puncture at point 18a is at an
acute angle to the surface of seal 12a. This tends to cause
puncture flaps 19a and 19b to be of unequal size since the
penetration of pointed tip 16 exerts unequal forces about point 18a
as sealing membrane 12a is punctured.
FIG. 4 is a schematic diagram of a similar lead tip employing the
present invention. Helical sealing membrane 12 has a formed portion
13 which is located normal to the direction of travel of pointed
tip 16. As pointed tip 16 punctures formed portion 13 of sealing
membrane 12, the puncture has a projection on formed portion 13
equal to dimension 20. A comparison of FIGS. 2 and 4 shows that
dimension 20a (See FIG. 2) is significantly larger than dimension
20 (See FIG. 4) because of the difference in puncture angle. The
practical significance is that dimension 20a must be sealed in FIG.
2 whereas only dimension 20 need be sealed in FIG. 4. The thickness
of the helical membrane 12, except formed portion 13, is enlarged
to the size of the spacing between the helical coil electrode, in
order to serve as a helical guide for the helical coil electrode
when being extended or retracted upon rotation.
FIG. 5 shows the structure with helical fixation coil extended.
Because pointed tip 16 punctures formed portion 13 at a right
angle, equal force is exerted in all directions. This tends to
cause flaps 19c and 19d to be of equal size. Perhaps even more
importantly, flaps 19c and 19d are each nearly perpendicular to
formed portion 13 causing maximum chronic sealing. A comparison
with FIG. 3 shows that flap 19a is at an acute angle and flap 19b
is at an obtuse angle. This disparity greatly affects chronic
sealing and impacts resiliency preventing effective sealing. This
configuration can be chosen, if the complete tip or the membrane 12
and formed portion 13 are made of silicon rubber.
FIG. 6 is a schematic drawing showing that the formed portion 13 of
sealing membrane 12 actually contains three layers. Layers 13a and
13c are polyurethane or other thermoplastic material. Layer 13b is
a non-stress relaxing material such as silicon rubber or medical
adhesive. This combination has been shown to provide good chronic
sealing, if the membrane 12 and housing 10 are made of polyurethane
or other thermoplastic material.
FIG. 7 is a front view of the distal tip of lead tip 10. Lead tip
10 is molded of polyurethane or other suitable material. From the
distal end, lead tip 10 has a cylindrical lumen 43 surrounded by
pillar 42 and outer housing 44, and bottomed by the sealing
membranes 12 and 13. Upon being extended, helical fixation coil 14
punctures sealing formed portion 13 of helical membrane 12 and
proceeds into cylindrical lumen 43 and outward into the
endocardium. Pillar 42, cylindrical lumen 43, and outer housing 44
are the distal end of a cylindrical lumen inside of lead tip 10
through which helical fixation coil 14 travels.
FIG. 8 is a side sectional view of lead tip 10, which is molded of
polyurethane as explained above. The cylindrical lumen is seen as
comprised of points 43, and pillar 42. This cylindrical lumen and
helical membrane 12 guide the movement of helical fixation coil 14
(not shown in this view). Formed portion 13a of sealing membrane 12
is shown by the dotted lines between the extremes of sealing
membrane 12 in axial direction, and between pillar 12 and housing
44 in radial direction. Formed portion 13a is originally molded
into the lead tip. Through formed portion 13a in a direction
approximately perpendicular to the sectional plane, the helical
coil electrodes will be punctured.
FIG. 9 is a sectional view taken perpendicular to the main axis of
lead tip 10 and parallel to formed portion 13a. Because formed
portion 13 is at an acute angle relative to the plane of the
sectional view, the layers 13a, 13b and 13c are all clearly
visible. Notice that layer 13a is as originally molded into lead
tip 10 being of the same material. Layer 13b is deposited onto
layer 13a. Layer 13b is preferably silicon rubber or medical
adhesive. Layer 13c is subsequently deposited on layer 13b. Layer
13c is preferably polyurethane or other thermoplastic material.
FIG. 10 shows a sectional cutaway view of sealing membrane 12
viewed parallel to the plane of formed portion 13. Cylindrical
lumen 43 is shown. Layer 13a is shown as a molded portion of lead
tip 10. Layer 13b is deposited on layer 13a distal to layer 13a.
Layer 13c is subsequently deposited on layer 13b.
* * * * *